Chemical properties of N‐Benzoylimines of quinazoline, quinoxaline, and phthalazine

Abstract

AbstractReactions of 1‐benzoylimino‐4‐phenylquinazolinium (I), 1‐benzoylimino‐3‐phenylquinox‐alinium (II), and 3‐benzoylimino‐1‐phenylphthalazinium betaines (III) with nucleophiles (hydroxide and cyanide ions) and 1,3‐dipolarophiles (acetylenic esters and maleimides) were investigated. Heating I in aqueous alkali gave 3‐phenylindazole, while similar treatment of II and III resulted in the formation of 1‐benzoylamino‐2‐oxo‐3‐phenylquinoxaline and 2‐benzoylamino‐1‐oxo‐4‐phenylphthalazine, respectively. Reaction of II and III with cyanide ion afforded 2‐cyano‐3‐phenylquinoxaline and 1‐cyano‐4‐phenylphthalazine in high yields, respectively. 1,3‐Dipolar cycloaddition reactions of I and III with dimethyl acetylenedicarboxylate and ethyl propiolate afforded primary 1:1 cycloadducts, while the reaction of II with dimethyl acetylenedicarboxylate gave a product which is formed by ring opening of a primary adduct. The reaction of I‐III with N‐methyl and N‐phenylmaleimides afforded the corresponding primary 1:1 cycloadducts in high yields, whose stereochemical assignment was made on the basis of nmr spectroscopy.